Data from published studies of the quantity of medroxyprogesterone acetate and/or its metabolites in the milk of lactating women receiving Depo-Provera for contraception is extrapolated into the amount of drug ingested daily by a theoretically average infant. Comparisons are made with the results of similar studies in animals. Fetal metabolism of medroxyprogesterone acetate is reviewed. Embryonic and fetal development of the human reproductive system is discussed. Results of studies of the effects of steroidal hormones, particularly medroxyprogesterone acetate, on mental development and sexual dimorphic behavior after exposure in utero are presented. It is concluded that the very small amount of drug and/or its metabolites ingested by the nursing infant via breast milk is highly unlikely to have any significant effect on the nursing infant.